Breast cancer (BC) is a complex disease, characterized by heterogeneity of genetic alterations and influenced by several environmental factors. Ductal carcinoma in situ (DCIS) is a heterogeneous group of lesions reflecting the proliferation of malignant cells within the breast ducts without invasion through the basement membrane. About 80% of all breast cancers are invasive ductal carcinomas (IDC), the most frequent type of BC. Breast tumors of distinct molecular subtypes (luminal A/B, HER2+, and basal-like) have dramatically different mRNA profiles.
Until 1980, DCIS was diagnosed rarely and represented <1% of BC. With the increased use of mammography, DCIS became the most rapidly increasing subset of BC, accounting for 15%-25% of newly diagnosed BC cases in the US.
MicroRNA (miRNA) is a class of conserved non-coding RNAs with regulatory functions, which exerts important roles in cancer. Microarray analysis of miRNAs has been generating much new knowledge in recent years. There is still a need for information about the function and activity of miRNAs, as well as for methods and compositions that can be used for their characterization and analysis. However, genome-wide mRNA expression studies failed to identify progression stage-specific genes.